Arianespace Soyuz ST-B successfully launches four O3b satellites

The Arianespace Soyuz ST-B rocket has launched her mission to loft four O3b communication satellites into orbit on Thursday. The spacecraft are heading to a constellation that is already populated by eight of the birds controlled by O3b Networks. Lift off from the European Spaceport in Kourou, French Guiana occurred at 18:37 UTC.

The more powerful Soyuz-ST configuration is the standard version launched from French Guiana, with the additional performance provided by the Soyuz ST-B variant – including a Fregat-MT upper stage.

The Soyuz-2 was developed from the older Soyuz models, and features digital flight control systems and modernised engines. It first flew in 2004.

Two variants are currently in service; the Soyuz-2-1a, and the Soyuz-2-1b which features an RD-0124 third stage engine which provides additional thrust. The RD-0124 was declared operational on 3 May 2011.

A third configuration, the Soyuz-2-1v, debuted at the end of last year. It features an NK-33 engine in place of the RD-108A used on the core stages of the other configurations, and does not include the strapon boosters used by other configurations.

The Soyuz-2 forms the basis for the Soyuz-ST rocket, which is optimised to fly from Kourou, and also incorporates a flight termination system and a modified telemetry system.

The RD-0124 is a staged-combustion engine powered by a multi-stage turbopump, which is spun by gas from combustion of the main propellants in a gas generator. These oxygen-rich combustion gases are recovered to feed the four main combustion chambers where kerosene – coming from the regenerative cooling circuit – is injected.

Attitude control is provided by main engine activation along one axis in two planes. Liquid oxygen (LOX) and kerosene tanks are pressurized by the heating and evaporation of helium coming from storage vessels located in the LOX tank.

Avionics for the Soyuz launcher are carried in the vehicle’s third stage, and are located in an intermediate bay between the oxidizer and fuel tanks.

As part of the Soyuz’ upgrades for its operations from the Spaceport, the launcher’s flight control system is modernized with a digital control system.

This system incorporates a digital computer and inertial measurement unit that are based on proven technology – giving the Soyuz improved navigation accuracy and control capability.

The new digital control system provides a more flexible and efficient attitude control system, and it gives the additional flight control authority required for the new, enlarged Soyuz ST payload fairing.

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In addition, it improves flight accuracy for the Soyuz’ first three stages, and provides the ability to perform in-flight roll maneuvers as well as in-plane yaw steering (dog-leg) maneuvers.

The Fregat upper stage is an autonomous and flexible upper stage designed to operate as an orbital vehicle. Flight qualified in 2000, it extends the Soyuz launcher’s capability to provide access to a full range of orbits (medium-Earth orbit, Sun-synchronous orbit, geostationary transfer orbit, and Earth escape trajectories).

Fregat consists of six spherical tanks arrayed in a circle (four for propellant, two containing the avionics), with trusses passing through the tanks to provide structural support. The stage is independent from the Soyuz’ lower three stages, having its own guidance, navigation, control, tracking, and telemetry systems.

The Fregat uses storable propellants (UDMH/NTO) and can be restarted up to 20 times in flight – enabling it to carry out complex mission profiles. It can provide 3-axis stabilization or perform a spin-up of the spacecraft payload.

The Fregat first flew in 2000, and has been used on Soyuz-U, Soyuz-FG, Soyuz-2 and Zenit rockets.

The launch was performed from the purpose-built ZLS launch facility for Soyuz – located in the Spaceport’s northern sector near the city of Sinnamary.

The Spaceport’s Soyuz launch site combines the proven design elements from the long-existing site at Baikonur Cosmodrome with satellite integration procedures that are in concert with the spacecraft processing used for Ariane missions.

Located 12 kilometers northwest from the existing Ariane 5 launch complex, the new Soyuz facility extends the Spaceport’s operational zone further up the French Guiana coastline.

The launch vehicle’s assembly building is 92 meters long, 41 meters wide, and 22 meters tall, allowing the vehicle to be assembles horizontally, prior to rolling out to the launch site, which is configured after the Russian Baikonur and Plesetsk Cosmodromes, albeit with a new mobile launch service tower.

The Soyuz’ transfer to the Spaceport’s launch zone is performed with the launcher riding horizontally atop a transporter/erector rail car.

Soyuz was then raised into position on the pad, and in contrast with the Baikonur Cosmodrome processing flow, is protected by a gantry that moves into place for payload integration.

The latest O3b Networks spacecraft were deployed by Soyuz into a circular orbit at an altitude of 8,062 km. – which is four-times closer to Earth than traditional geostationary satellites, providing substantial performance benefits due to lower latency or delay.

O3b Networks initiated commercial service on its state-of-the-art constellation across the Pacific, Africa, the Middle East and Asia in September of this year, and it already is delivering more than 4 Gbps of high quality connectivity to customers across the globe.

O3b’s Ka-band satellites were built by prime contractor Thales Alenia Space. The total flight duration to get them to their separation point took two hours and 22 minutes.

The spacecraft have a trapezoidal-shaped main body, which helped facilitate their integration on the payload system, which is a tube-shaped dispenser system, with the satellites mated to the upper and lower attach points.

The previous two Arianespace Soyuz missions for O3b Networks also lofted four spacecraft each on launches performed in July 2014 and June 2013.